15 replies to this topic

[formula.crazy]

Anybody to help will be excellent.
Please please give in SI units.

Question is,
a heating tank ( approx 1.2m tall and 0.86m Diameter) will have a flow of 1000kg per hour of oil running through. It needs heating of 50 to 65 deg. With about 3 bar steam running through the heating coil.
What length should the coil would be sufficient?

Tell me what else info you need?

Edited by formula.crazy, 20 November 2012 - 02:15 PM.

[ankur2061]

formula crazy,

My consultation fee for doing the calculation is a very nominal $150/-. Let us agree on the mode of payment and and I will send you the calculations including the results. Obviously some more inputs may be required such as properties and pressure and temperature conditions of the vegetable oil. These are standard engineering consultation charges and I am sure that since your are in a hurry and don't have the time to either personally do or review these calculations you will agree to my proposal.

Hoping to hear from you.

Regards,
Ankur

[formula.crazy]

Didnt know this forum charged.
Sorry, i cannot afford that.
Anybody else?

[ankur2061]

formula crazy,

Well you can't afford that but you do expect somebody else to do your work for free and hand it over to you so that you can present it to your boss and claim it as your work.

I could have understood if you had done some work on your own and asked somebody to review it and make suggestions for corrections which many would have come forward to help.

How fair do you think it is??

Edited by ankur2061, 20 November 2012 - 08:32 AM.

[J_Carlos]

Formula crazy,

It's not that difficult to consult a proper ChemEng book (such as Perry's or Coulson...). There you can find detailed info about heating coils design. You can also consult other threads in this forum, I'm sure Art Montgomery has already posted a spreadsheet about this topic.

Br, JCarlos

[formula.crazy]

im busy trying to figure out at that moment from the net, pulling out hairs...., have no perrys our coulson with me.
Trying . .. .

[formula.crazy]

if there's anybody willing to assist, it would be nice to hear from you.

[Art Montemayor]

Crazy:

I believe EVERYONE on the Forums would want to help you. Giving you free, consulting engineering time and calculations is not help - that is nothing but a pure "handout" (or free engineering). Our Forums are structured and maintained for helping other engineers and engineering students. We also help a lot of non-engineers - but those are technicians and operators who make the effort to learn engineering and the theory as well as how it is applied. We have helped a lot of non-engineers in the past - but not by solving their problems directly. We help them solve their own problems by examining and reviewing their submitted work and calculations.

I (and probably all of our forum) can easily resolve your problem. All you need is a 20 foot length of 1-1/2" schedule steel pipe rolled in the form of a coiled spiral and immersed in your tank. However, there is a lot more to the application than just that information. If I were to donate my calculations and sketches on how to build the coil, install it, and operate it, it would be "free" engineering. That's not what our Forum is here for. I hope you can understand the professional position of our Forums' professional engineers.

[kkala]

1. It is noted that formula.crazy is in a hurry, results had better be supported by calculations, only length of coil is requested (not detailed engineering). It could have been more convenient, if he could have started the effort earlier. At any case jokes on fee have nothing to do with the topic.
2. Sizing the heating coil as above is not so easy, see http://www.cheresources.com/invision/topic/13699-how-to-get-value-of-heat-transfer-coefficient/. This can be used as example for your calculation, although the new case is not identical.
3. Steam side heat transfer coefficient (~8500 W/m2/oC) is not the controlling factor in this heat transfer, this of the (vegetable?) oil side is. The latter has to be calculated (better option, any help on this welcomed); or else we have to adopt something out of Perry's data, as in the example. Fouling factor has also to be considered. Tank is assumed uninsulated, top closed, located in a room, without agitation (nothing mentioned about it).
4. Start with a heat balance. If the oil has to be heated from 20 to (55-) 65 oC, supplied heat equals to
α) oil heating 1000*2*(65-20)=90000 kJ/h = 25 kW (assumed Cp=2 kJ/kg/oC, Perry, spec heats of misc materials, oils)
β) heat losses to ambient (18 oC). Assuming overall U=15 W/m2/oC (*), 15*3.8*(65-18)=2679 W = 3 kW
so total heat supplied Q= 28 kW = 101000 kJ/h, corresponding to 47.4 kg/h of condensing steam (latent heat=2133 kJ/kg, 4 bara).
(*) see http://www.cheresources.com/invision/topic/14965-vessel-heat-loss
5. For the heating coil to be sized: Q=28 kW, temper difference Δt= 143-65=78 oC. Assuming U=23 Btu/ft2/h/oF = 130 W/m2/oC (including scales), heating coil surface required = 2.76 m2. Assuming 1.5" coil, its total length would be 2.76/0.1516=18.2 m ~ 20 m. Result differs to prediction of post No 8, but if ingoing oil temperature were assumed 65 oC, length of 1.5" coil would be only 2 m . It depends on the assumed data, to be correctly adopted by formula.crazy.
6. Of course above results are imprecise, intending only to show a way. Correct data has to be adopted. Comments are very welcomed, general or on the assumptions.
Present post hopefully helps this urgent case.

Edited by kkala, 20 November 2012 - 06:16 PM.

[Art Montemayor]

Kkala:

I did all my homework before I wrote my post. My detailed calculations show that what I wrote will work; otherwise I wouldn't have said anything. The point I tried to make is that getting the answer is relatively easy; but the answer is not worth much without the backup calculations and justification.

[ankur2061]

I can't think of squeezing a 18-20 m length coil in a 1.2 m tall tank and with 0.86 m diameter even in a helix configuration. 20 ft seems to be a more reasonable figure for such a small tank.

Any assumptions required for sizing calculations need to be backed up by data for similar design otherwise they just remain assumptions (ass-u-me).

[kkala]

For the heating coil to be sized: Q=28 kW, temper difference Δt= 143-65=78 oC. Assuming U=23 Btu/ft2/h/oF = 130 W/m2/oC (including scales), heating coil surface required = 2.76 m2. Assuming 1.5" coil, its total length would be 2.76/0.1516=18.2 m ~ 20 m. Result differs to prediction of post No 8, but if ingoing oil temperature were assumed 65 oC, length of 1.5" coil would be only 2 m . It depends on the assumed data, to be correctly adopted by formula.crazy.
Of course above results are imprecise, intending only to show a way. Correct data has to be adopted. Comments are very welcomed, general or on the assumptions.
Present post hopefully helps this urgent case.

Query had many points needing clarification, but it was urgent according to post No 1 before editing. So assumptions were made for the conditions (e.g. inlet oil temperature, ambient air temperature), to be eventually modified by formula.crazy. Assumed heat transfer coefficients are judged to be in the ball park and supported by mentioned references, Perry or Cheresources threads. Coil overall U=23 Btu/ft2/h/oF is not arbitrary, "the latter has to be calculated (better option, any help on this welcomed); or else we have to adopt something out of Perry's data, as in the example". Perry (7th ed, table 11-2 ) reports U=23-29 Btu/ft2/h/oF for steam coil to heat vegetable oil without agitation.
Post No 10: Stating assumptions made in the calculation would have helped to trace arithmetic differences between posts No 9 and 10. Besides OP (formula.crazy) could revise them, concerning conditions.
Post No 11: 1.5" coil diameter was assumed for comparison. 8 x 1.5" spire in 1.2 m height may or may not be feasible, yet 1 spire is adequate if oil inlet and outlet temperatures are same. Coil squeezing (if any) could be addressed, when actual data replace assumptions. Present aim is a way to estimate coil heating surface, not subject to decrease for a given tank.
"ass-u-me" is found to be abusive, http://www.urbandict...php?term=assume '> http://www.urbandict...php?term=assume . This is the reason of placing negative feedback. Besides it is unfair, assumptions are adequately backed-up for the case.

[kkala]

I can't think of squeezing a 18-20 m length coil in a 1.2 m tall tank and with 0.86 m diameter even in a helix configuration. 20 ft seems to be a more reasonable figure for such a small tank.
Any assumptions required for sizing calculations need to be backed up by data for similar design otherwise they just remain assumptions (ass-u-me).

Noted. Argumentation has been developed in post No 12 by kkala.
The reader can google "ass-u-me", then find its meaning in the urban dictionary, top.

[kkala]

Ankur2061 is requested to give public explanations for the negative feedback to the above post, placed soon after kkala placed negative feedback to Ankur's post No 11. But reasons for the latter feedback were explained in public by kkala, post No 12.

Edited by Art Montemayor, 21 November 2012 - 07:49 PM.

[ankur2061]

kkala,

I will repeat once again that as per the rules of the forum a public explanation will not be provided for the negative feedback. See your personal messenger for an explanation on the negative feedback.

[kkala]

kkala,I will repeat once again that as per the rules of the forum a public explanation will not be provided for the negative feedback. See your personal messenger for an explanation on the negative feedback

A rule compelling members to private communication after a (public) negative feed back would have been unilateral and against freedom of speech. This is noted (to no avail so far) in http://www.cheresources.com/invision/topic/16523-preventing-crude-oil-sludge/, post No 6.
A private communication between people of good will to eliminate errors or misunderstandings is not bad, as an option. Even in this case, public justification should get mandatory if one of the two parties requests it. Let us not use it as a pretext.
Have I deviated a rule by stating the reason of negative feedback to post No 11? I consider "ass-u-me" too heavy and negative feedback by return too much, so public justification is needed.
Ankur2061 is requested to publish reasons for negative feedback on kkala's post No 13.
Same for negative feedback on kkala's post No 6 in "Preventing Crude oil sludge" mentioned above.

Edited by kkala, 22 November 2012 - 06:39 AM.